1. Field of the Invention
The present invention relates to the light source of non-luminescence display devices, and more particularly, to a liquid-crystal display device having a backlight provided with a light guide and that uses an LED as a light source.
2. Description of the Related Art
Liquid-crystal display devices have been frequently used as display devices in recent years. Particularly, liquid-crystal display devices have been used for the displays of portable devices because of their thin, lightweight, and energy saving features.
However, liquid-crystal display devices need lighting means because they are not of light-emitting type. Popular lighting units used in liquid-crystal display devices include planar lighting units called backlights. Cold-cathode fluorescence lamps have been generally used as the light-emitting devices (also referred to as light sources) of the backlights, while light-emitting diodes (LEDs) are also used as the light-emitting devices.
The backlights have a planar light guide. The light guide is made of light-transmissive resin or the like, so that light which is emitted from light-emitting devices and enters the light guide. The light guide transmits through the light. The light guide has reflecting or dispersing members such as grooves, protrusions, or prints. The reflecting or dispersing members cause the light that transmits through the light guide to advance toward the liquid-crystal display device.
The use of LEDs as light-emitting devices poses the problem of difficulty in letting out uniform light from the light guide because they are point light sources. To cope with such a problem, for example, JP-A-2002-169034 proposes a technique of dispersing the light around the LEDs evenly in which the light incident surface of the light guide has notches.